The primer used for aircraft was zinc chromate which is a flat green typically. Although there can be some variation due to applicators not alway getting the paint throughly mixed and sometimes vendors had slightly different formulations. Some zinc chromates look almost yellow in some cases.

HEY GUY'S IT'S ACCUALLY CALLED ZINC CHROMATE YELLOW THE VARIATIONS OF COLOR WAS FROM DIFFERENT BATCHES OF PAINT THAT DIDN'T HAVE THE SAME AMOUNT OF COLOR MIXED IN IT WHEATHER IT WAS TO MUCH OR NOT ENOUGH GAVE IT IT'S TONE OF GREEN OR YELLOW IT WAS ACCUALLY JUST A PRIMER.

Zinc Chromate was the only primmer that would stick to Alumimun in the early years now there is Epoxy. It comes it two colors Green and Yellow. I have painted many Real Aircraft over the years. When I was In the Navy stationed at NAS Miramar I was Petty Officer in charge of the base aircraft paint shop. You can still order Zinc Chromate from aircraft suppliers. Always wear a good Paint mask with this and all paints. BOB MOORE AMA 6559

Go to your local auto paint store that sells Sherwin Williams Acrylic Enamel.
Tell the guy you want 1 pt of Fleet WA5755 number 35-3968800 green.
1pt for $26.19...that will be enough to paint about a hundred firewalls and retract holes.
Jim

Green Zinc Chromate and Yellow Zinc Chromate were used as anti-corrosion primers on the interior of panels and such. Cockpits might have a zinc chromate primer but would usually be overpainted with normal paint (eg. Interior Green).

Testors Model Master paints have very good enamels in these colours but, you should thin them and airbrush for decent coverage. If you're doing wheel wells and engine bays one bottle should be more than enough. However, if you plan on covering a large surface area take a painted sample (of the model paint) to the local paint store and have them colour match it as this is much cheaper.

If you want the real thing try Zinc Chromate Primer. I found it at Ace Hardware but since it is a marine paint any hardware or supply house that caters to the marine industry should have it. Made by Tempo Products Company Inc. PO Box 39126 Cleveland, Ohio. Part number 020421/Model Number 5605, 12 ounce spray can about $8.00.